1. Field of the Invention
This invention relates in general to electrostatic copiers.
More particularly, the invention relates to developer devices used in electrostatic copiers.
Still more specifically, the invention relates to an arrangement for supplying toner to such developer devices.
2. The Prior Art
In electrostatic copiers a latent image of electrostatic charges of an original to be copied is produced on the photosensitive surface of a travelling image carrier, typically a rotating copy drum. Thereafter, this image is developed by electrostatically attracting toner particles to it which are then, during further travel of the image carrier, transferred to a copy sheet on which they form a visible image.
Because the supply of toner is used up in making copies, it must be periodically renewed. In one type of copier this is done by pouring fresh toner into the receptacle provided for this purpose in the developer device of the copier. This makes for rather grimy conditions since parts of the copier which in normal use are touched by an operator, become inevitably soiled with toner. Furthermore, there is no way in which the user can readily switch from one type of toner to another, as is sometimes necessary in dependence upon particular copying requirements.
To alleviate some of these problems it has been proposed, in another type of copier, to supply the toner in one-way (i.e., throw-away) containers. These have an opening which is closed by a foil or the like. When such a container is to be used the foil is ruptured as the container is installed on the developer device, with its opening facing in downward direction so that toner from the container is gravity-fed to the developer device. When the toner in the container is used up, the empty container is replaced with a full one.
A drawback of this arrangement is that once the foil is ruptured there is no way to remove the container from the copier without encountering the same soiling problem as in the first-mentioned type of copier. This stands to reason since the downwardly facing opening of the container cannot be reclosed and the toner remaining in the container will inevitably drop out when the container is removed. From time to time there is, however, a definite need to remove such a container even if it is not yet empty, namely if the developer device needs to be serviced or if it is desired to be able to use a different kind of toner.
A rather expensive solution to this problem proposes to construct the container and the toner dosing (metering) device--which normally forms part of the developer device--as a single unit. This does permit the removal of such a mist without soiling of the copier, even if the container is not yet empty of toner material. However, in this construction the dosing device must be discarded together with the container when the same is emptied of toner, and the resultant higher costs and waste of materials are not compensated-for by the increased operating convenience.